O R I G I N A L A R T I C L E UDC: 616-089:617-089.163 DOI: 10.2298/VSP1305484V
Myocardial protection during elective coronary artery bypasses
grafting by pretreatment with omega-3 polyunsaturated fatty acids
Zaštita srca tokom operacije revaskularizacije sr
þ
anog miši
ü
a primenom
omega-3 nezasi
ü
enih masnih kiselina
Miliü Veljoviü*†, Ana Popadiü*, Zoran Vukiü*, Radoje Iliü†‡, Zoran Trifunoviü‡, Mirjana Antunoviü†§, Vladimir Mandariü‡, Svetislav Tišma‡,
Zoran Markoviü‡
*Clinic of Anesthesiology and Intensive Care, ‡Clinic of Cardiac Surgery, Military Medical Academy, Belgrade, Serbia; §Sector of Pharmacy, Military Medical Academy, Belgrade, Serbia; †Faculty of Medicine of the Military Medical Academy, University of
Defence, Belgrade, Serbia
Abstract
Background/Aim. Despite recent advances in coronary ar-tery bypass grafting (CABG), cardioplegic cardiac arrest and cardiopulmonary bypass (CPB) are still associated with myo-cardial injury. Accordingly, the efforts have been made lately to improve the outcome of CPB by glucose-insulin-potassium, adenosine, Ca2+-channel antagonists, L-arginine,
N-acetylcysteine, coenzyme Q10, diazoxide, Na+/H+
ex-change inhibitors, but with an unequal results. Since omega-3 polyunsatutated fatty acids (PUFAs) have shown remarkable cardioprotection in preclinical researches, the aim of our study was to check their effects in prevention of ischemia re-perfusion injury in patients with CPB. Methods. This pro-spective, randomized, placebo-controlled study was performed with parallel groups. The patients undergoing elective CABG were randomized to receive preoperative intravenous omega-3 PUFAs infusion (n = 20) or the same volume of 0.9% saline solution infusion (n = 20). Blood samples were collected si-multaneously from the radial artery and the coronary sinus be-fore starting CPB and at 10, 20 and 30 min after the release of the aortic cross clamp. Lactate extraction/excretion and myo-cardial oxygen extraction were calculated and compared be-tween the two groups. The levels of troponin I (TnT) and cre-atine kinase–myocardial band (CK-MB) were determined be-fore starting CPB and 4 and 24 h postoperatively. Results. Demographic and operative characteristics, including CPB and aortic cross-clamp time, were similar between the two groups
of patients. The level of lactate extraction 10 and 20 min after aortic cross-clamp time has shown negative values in the con-trol group, but positive values in the PUFAs group with statis-tically significant differences (-19.6% vs 7.9%; p < 0.0001 and -19.9% vs 8.2%; p < 0.0008, respectively). The level of lactate extraction 30 minutes after reperfusion was not statistically dif-ferent between the two groups (6.9% vs 4.2%; p < 0.54). Oxy-gen extraction in the PUFAs group was statistically significantly higher compared to the control group after 10, 20 and 30 min of reperfusion (35.5% vs 50.4%, p < 0.0004; 25.8 % vs 48.7%, p
< 0.0001 and 25.8% vs 45.6%, p < 0.0002, respectively). The level of TnT, 4 and 24 h after CPB, was significantly higher in the control group compared to PUFAs group, with statistically significant differences (11.4 vs 6.6, p < 0.009 and 12.7 vs 5.9, p < 0.008, respectively). The level of CK-MB, 4 h after CPB, was significantly higher in the control group compared to PUFAs group (61.9 vs 37.7, p < 0.008), but its level, 24 h after CPB, was not statistically different between the two groups (58.9 vs 40.6, p
< 0.051). Conclusion. Treatment with omega-3 PUFAs ad-ministered preoperatively promoted early metabolic recovery of the heart after elective CABG and improved myocardial pro-tection. This study showed that omega-3 emulsion should not be considered only as a nutritional supplement but also as a clinically safe and potent cardioprotective adjunct during CPB.
Key words:
fatty acids, omega-3; myocardial reperfusion; coronary artery bypass; surgical procedures, elective.
Apstrakt
Uvod/Cilj. Uprkos tehnološkom napretku srÿani zastoj izaz-van kardioplegijom i izaz-vantelesni krvotok (cardiopulmonary bypass
– CPB) tokom operacije revaskularizacije srÿanog mišiýa i da-lje dovode do ošteýenja srÿanog mišiýa. Napor da se poboljša
ishod posle CPB primenom glukoze-insulin-kalijuma, adeno-zina, blokatora Ca2+-kanala, L-arginina, N-acetilcisteina,
ko-enzima Q10, diazoksida, inhibitora razmene Na+/H+ nije dao
željene rezultate. Omega-3 nezasiýene masne kiseline
ovog rada bio je ispitivanje efekata primene PUFA u preven-ciji ishemijsko reperfuzionih ošteýenja srÿanog mišiýa nakon revaskularizacije sa primenom CPB. Metode. Ova prospekti-vna, randomizovana, placebo-kontrolisana studija sprovedena je na paralelnim grupama. Bolesnici sa elektivnim operacijama revaskularizacije srÿanog mišiýa sluÿajnim izborom podeljeni su u dve grupe. Prva grupa (n = 20) preoperativno je dobijala infuziju PUFAs (PUFAs grupa), dok je kontrolna grupa (n = 20) dobijala istu koliÿinu 0,9% rastvora NaCl. Uzorci krvi su istovremeno uzimani iz radijalne arterije i koronarnog sinusa pre poÿetaka CPB i 10, 20 i 30 minuta posle skidanja kleme sa aorte. Ekstrakcija laktata i kiseonika iz srÿanog mišiýa izvede-na je primenom pozizvede-natih formula. Nivo troponiizvede-na I (TnT) i miokardne frakcije kreatin-kinaze (CK-MB) odreĀivana je pre poÿetka CPB i 4 i 24 h posle operacije. Rezultati. Demograf-ske i operativne karakteristike, ukljuÿujuýi trajanje CPB i kle-movanja aorte, bili su sliÿni u obe grupe. Nivo ekskrecije lak-tata 10 i 20 min nakon deklemovanja aorte imao je negativne vrednosti u kontrolnoj grupi, dok su vrednosti u PUFAs gru-pi bile pozitivne, sa statistiÿki znaÿajnom razlikom (-19,6% prema 7,9%; p < 0,0001 i -19,9% prema 8,2%; p < 0,0008, re-spektivno). Nivo ekstrakcije laktata 30 min nakon skidanja kleme sa aorte bio je bez statistiÿki znaÿajne razlike izmeĀu
dve grupe (6,9% prema 4,2%; p < 0,54). Ekstrakcija kiseonika 10, 20 i 30 min posle skidanja kleme sa aorte bila je veýa u PUFAs grupi sa statistiÿki znaÿajnom razlikom u odnosu na kontrolnu grupu (35,5% prema 50,4%, p < 0,0004; 25,8 % prema 48,7%, p < 0,0001 i 25,8% prema 45,6%, p < 0,0002, respektivno). Nivo TnT, 4 i 24 sata nakon CPB, bio je statis-tiÿki znaÿajno viši u kontrolnoj grupi nego u PUFAs grupi (11,4 prema 6,6 ng/mL p < 0,009 i 12,7 prema 5,9 ng/mL p
< 0,008). Nivo CK-MB, 4 h nakon CPB, bio je statistiÿki znaÿajno viši u kontrolnoj grupi nego u PUFA grupi (61,9 prema 37,7 U/L; p < 0,008), dok je nivo CK-MB 24 h nakon CPB bio bez statistiÿki znaÿajne razlike izmeĀu dve grupe bolesnika (58,9 prema 40,6 U/L; p < 0,051). Zakljuÿak. Pre-operativna primena omega-3 PUFAs pomaže u ranom meta-boliÿkom oporavku srca nakon revaskularizacije tako što štiti srÿani mišiý. Ovo istraživanje je pokazalo da omega-3 PUFAs nisu samo nutricioni dodatak veý i kliniÿki bezbedan i snažan kardioprotektor tokom CPB.
Kljuÿne reÿi:
masne kiseline, omega-3; miokard, reperfuzija; aortokoronarno premošýavanje; hirurgija, elektivna, procedure.
Introduction
Myocardial protection by using hypothermia and cardio-plegia methods during ischemia and reperfusion remains one of the cornerstones of postoperative myocardial function. Coro-nary artery bypass grafting (CABG) performed with the aid of cardioplegia and cardiopulmonary bypass (CPB) requires a pe-riod of cardiac arrest. During this time, myocardial ischemia and necrosis may occur, which is an important determinant of functional and clinical outcome 1. Despite CPB techniques as well as postoperative intensive care improvement impaired myocardial function is well-documented as a complication of CPB, resulting in increased morbidity and mortality 2–4.
With increasing complexity of adult and pediatric cardiac surgical procedures, complete myocardial protection is prov-ing a challenge. Attempts to provide additive cardioprotection to date has met with little benefit in clinical trials. Most new therapies, such as sodium/hydrogen exchange inhibitors 5, glu-cose-insulin–potassium 6, adenosine 7, Ca2+-channel antago-nists 8, L-arginine 9, N-acetylcysteine (NAC) 10, coenzyme Q10 11, diazoxide 12, corticosteroids 13, pexelizumab 14 have fo-cused on a single aspect of pathologic ischemia-reperfusion injury, with unequal benefit.
It is experimentally and clinically well established that long-chain omega-3 polyunsaturated fatty acids (PUFAs) protect against and can terminate ischemic arrhythmias 15, 16. Their anti-inflammatory effects, which include attenuation of leukocyte-endothelial interactions and production of less biologically active prostaglandins and leukotrienes, could also be beneficial in cardiac ischemia-reperfusion injury 17–19. Furthermore, clinical trials have shown that omega-3 PUFAs pretreatment induces heat shock proteins (HSP) in the myo-cardium, protecting against ischemia, suggesting a precondi-tioning phenomenon 20. One other potential mechanism of
action of PUFAs would be that they act as a “sink” to trap free radicals, hence becoming oxidized themselves 21. The susceptibility of fatty acids to oxidation is thought to be di-rectly dependent on their degree of unsaturation. Docosahex-aenoic acid (DHA)-mediated inhibition of interleukin (IL)-1-induced reactive oxygen species (ROS) production, would contribute to the anti-inflammatory actions of omega-3 PU-FAs at the endothelial level 22. Also, omega-3 PUFAs for clinical use and normally given as part of parenteral nutri-tion, led to myocardial protection administered in the acute setting 23. In selecting the possible mechanism of observed protection, we focused on the effects of incorporating the PUFAs into the myocardial membrane, a process shown to be important in their antiarrhythmic effect 24, 25.
The aim of this study was to assess the impact of omega-3 PUFAs, as eicosapentaenoic acid (EPA) and DHA, infusion therapy on early metabolic recovery of the heart during elec-tive CABG, leading to better myocardial protection.
Methods
This prospective, randomized, placebo-controlled study was performed with parallel groups. Study enrollment oc-curred between August 2010 and September 2011. The study protocol was approved by the Ethical Committee of the Military Medical Academy, Belgrade, and all the patients gave written informed consent.
un-stable angina, or poor left ventricular function. All the patients were treated by the same surgical and anesthesiologist team.
Eligible patients were assigned to one of the two study arms according to a computer-generated randomization list: con-trol (placebo) group (usual care), and usual care plus PUFAs.
The PUFAs infusion consisted of 100 mL of a lipid emulsion with a high content of omega-3 PUFAs (Omegaven® 10%, Fresenius Kabi, Bad Homburg, Germany). The same batch of Omegaven® was used throughout the study, and 100 mL of the lipid emulsion contained 1.25–2.82g EPA and 1.44– 3.09 DHA. Infusion was given one day before surgery and re-peated 4 h before starting CPB via the peripheral vein at single doses of 100 mL (25 mL/h). The patients of the control group received an equal volume of 0.9% saline.
Preoperative sedation with 5 mg of intramuscular mida-zolam was administered to the patients on call to the operat-ing room. All the patients received prophylactic preoperative antibiotics (cefazolin, 2 g preincision and 2 g post-CPB; or if allergic to penicillin, vancomycin, 1 g preincision and 500 mg post-CPB). The same anesthesiologist administered stan-dardized total intravenous anesthesia using sufentanil, mida-zolam, propofol and pancuronium.
Immediately before CPB, 300 IU/kg heparin was ad-ministered intravenously, followed by additional doses as necessary to maintain an activating clotting time exceeding 500 sec. Protamine was administered as 1 mg/100 IU of the heparin dose after complete separation from CPB.
All the patients had CABG with the use of CPB, which was conducted with a roller pump and a membrane oxy-genator primed with a solution. During CPB, pump flow was set at 2.4 times the body surface area, and mean arterial pres-sure maintained between 50 and 60 mmHg. Temperature was allowed to drift with active rewarming at the end of CPB. Myocardial protection was afforded with cold potassium cardioplegia. A single-clamp technique was used, and car-dioplegia was given in an anterograde fashion. In all the pa-tients, the left internal mammary artery harvested and anas-tomosed to the left anterior descending artery. The rest of the grafts were constructed using the great saphenous vein.
After total release of the aortic cross-clamp, epicardial atrial or ventricular pacing wires were placed. Aortic and ve-nous cannulas were removed after thr appropriate test dose of protamine, and the surgery proceeded with closure of the pericardium and sternum.
After the surgery, the patients were followed up in the intensive care unit and were weaned off mechanical
ventila-tion when they fulfilled the following criteria: hemodynamic stability, peripheral temperature of more than 36°C, coop-eratively, and no major bleeding.
A retrograde perfusion cannula was used to collect si-multaneous blood samples from arterial blood and the coro-nary sinus just before commencing CPB and at 10, 20 and 30 min after the release of the aortic cross-clamp. These sam-ples were used to determine lactate concentration, hemoglo-bin (Hb) concentration, and oxygen saturation (O2 Sat).
Lactate extraction was calculated as the difference be-tween arterial and coronary sinus lactate content 26.
A negative value indicates lactate excretion, while the positive one indicates lactate uptake.
Oxygen content in both arterial and coronary sinus blood was calculated using the formula: 1.38 u H b u O2 Sat.
The arterial – coronary sinus oxygen content difference was calculated and its ratio to arterial oxygen content repre-sented oxygen extraction.
The levels of troponin (TnT) and creatine kinase myo-cardial band (CK-MB) concentrations were measured 4 and 24 h postoperatively as an indicator of myocardial protection.
The results were presented as mean values with a standard deviation. Significant differences between the study subject groups were analyzed using the t-test. Due to a great variability of some data, the Wilcoxon matched pairs test and Mann-Whitney U-test were also used. Comparison between more than two groups was done by using the Kruskal-Wallis test.
A p value of less than 0.05 was taken to be significant. The obtained data were processed using the Stat for Win-dows, R.4.5. Software package.
Results
The results of the study are presented in Tables 1 and 2 and Figures 1–4, divided in six parts: demographic and op-erative characteristics of patients, the influence of PUFAs on lactate and oxygen extraction, a relative relationship between lactate and oxygen extraction, the influence of PUFAs on se-rum levels of TnT and CK-MB, the coefficient of correlation (r) values, and peri- and postoperative complications.
Demographic and operative characteristics of the patients with CPB
Table 1 shows that the physical characteristics of the patients of the two studied groups (age, weight and height) were very similar, beeing also the case with LVEF and
op-Table 1 Baseline and operative characteristics of the patients in the PUFAs and the control group
Parameter Control group PUFAs group p
Age (years) , ʉ ± SD 62.4 ± 7 65.3 ± 8 0.56
Gender, male/female (n) 18/2 17/3 0.36
Weight (kg), ʉ ± SD 89.8 ± 6 92.1 ± 5 0.48
Height (cm), ʉ ± SD 176.4 ± 4 178.5 ± 3 0.06
LVEF (%), ʉ ± SD 54 ± 6 53 ± 9 0.10
CPB (min), ʉ ± SD 101.4 ± 21 95.5 ± 17 0.29
Aortic cross-clamp time (min), ʉ ± SD 42.5 ± 9 38.9 ± 8 0.66
CABG (number), ʉ ± SD 2.9 ± 0.8 2.8 ± 0.7 0.65
erative characteristics (CPB, time of the aortic cross-clamp and CABG number).
The influence of PUFAs on lactate and oxygen extraction in the patients with CPB
Table 2 shows that the results of both studied parameters – lactate and oxygen extraction – were opposite in the two groups of patients. Namely, lactate uptake before ischemia in the patients
in the control group was statistically significantly higher com-pared with the PUFAs group (36.7% vs23.9%; p < 0.01). The level of lactate extraction 10 and 20 min after aortic declamping had negative value in the control group compared with positive value in the PUFAs group with statistically significant differ-ences (-19.6% vs 7.9%; p < 0.0001 and -19.9% vs 8.2%; p < 0.0008, respectively). A negative value 10 and 20 min after aortic declamping indicated lactate excretion in the control group com-pared with the positive value in the PUFAs group which indi-cated lactate uptake. The level of lactate extraction 30 min after aortic declamping was not statistically different between the groups (6.9% vs 4.2%; p = 0.54) (Table 2). In contrast to this, the level of oxygen extraction increased in both groups of patients. Their peak values ranged from 22.9 ± 16.5% in the control group before CPB to 35.5 ± 8.5% 10 min after aortic declamping and from 29.5 ± 18.6% in the PUFAs group before CPB to 50.4 ± 5.2% 10 min after aortic declamping. The extraction of oxygen in
the PUFAs treated patients was highly statistically significant at all the three observed times after CPB in relation to the control group (with p ranging from 0.0001 to 0.0004).
A relative relationship between lactate and oxygen extraction
The relative relationship of lactate and oxygen extrac-tion, based on the values given in Table 2, with their initial
values before CPB marked as 100% and the percentage of their respective values at all the three observed time intervals after aortic declamping are presented in Figure 2, and show the time-course of their relative values.
It is self-evident from the results presented in this way that in the case of lactate extraction 10 min and 20 min after aortic declamping they diverge (plate A), and in those of oxygen extracton 10 min after aortic declamping converge, equalizing at 30 min after aortic declamping in the case of lactate, but not in the case of oxygen extraction (plate B).
The influence of PUFAs on the serum level of TnT and CK-MB
Figure 2 shows that the levels of TnT (plate A) and CK-MB (plate B) in both groups of patients were markedly higher at 4 h (p < 0.009 and p < 0.007). The level of troponin I, 24 h after CPB, was significantly higher in the control
Fig. 1 – Relative percentage versus time-relationship between lactate (A) and oxygen extraction (B) in the control and the polyunsaturated fatty acids (PUFAs) group of patients subjected to cardiopulmonary bypass (CPB) with the initial (basal)
values marked as 100%.
Table 2 Extraction of lactate and oxygen in the patients with CPB treated with omega-3 polyunsaturated
fatty acids (PUFAs) in relation to the control group with a standard protocol
Extraction (%), ʉ ± SD
Parameter Control group
(n = 20)
PUFAs group (n = 20)
p
Lactate before CPB 36.7 ± 18.3 23.9 ± 14 0.01
Lactate 10 min after CPB -19.6 ± 22.8 7.9 ± 20.5 0.0001
Lactate 20 min after CPB -19.9 ± 22.8 8.2 ± 27.1 0.0008
Lactate 30 min after CPB 6.9 ± 11.8 4.2 ± 21.9 0.54
Oxygen before CPB 22.9 ± 16.5 29.5 ± 18.6 0.3
Oxygen 10 min after CPB 35.5 ± 8.5 50.4 ± 5.2 0.0004
Oxygen 20 min after CPB 25.8 ± 9.7 48.7 ± 8.2 0.0001
Oxygen 30 min after CPB 25.8 ± 9.3 45.6 ± 8.7 0.0002
group as compared with the PUFAs group with statistically significant differences (12.7 versus 5.9 ng/mL p < 0.008) (Figure 2A). The level of CK-MB, 24 h after CPB was not statistically different between the groups (58.9 vs40.6 U/L p
< 0.051) (Figure 2B).
Concerning the relationship between the two groups, the serum level of TnT (plate A) was statistically signifi-cantly lower in the PUFAs treated patients in relation to the
control group at both observed times, being 72% (11.4 ng/mL: 6.67 ng/mL, p < 0.009) and 115% (12.7 ng/mL: 5.9 ng/mL, p < 0.008) lower at 4 hrs and 24 hrs after CPB, re-spectively. At the same time, the serum level of CK-MB (plate B) was also lower in the PUFAs treated patients at both observed time intervals of 4 h and 24 h after CPB, being 65% (61.9 U/L: 37.7 U/L, p < 0.007) and 45% (58.9 U/L : 40.6 U/L p < 0.051), respectively, in relation to the control group of patients.
Coefficient of correlation (r) values
Reliablity of described trends of the single values of all four parameters in both groups of patients were additionaly confirmed by the coefficient of correlation. Its calculation
was based on the values of parameters at all the observed time intervals (i.e. 10 to 30 min after aortic declamping in the case of lactate and oxygen extraction or 4 and 24 h after CPB in the case of TnT and CK-MB level) in relation to their initial (basal) values found before CPB.
In this respect, Figure 3 shows that the drop of lactate extraction (plate A) was uniform in both studied groups, but it was less pronounced in the the PUFAs group of patients.
Regarding oxygen (plate B), its level of extraction in the control group did not change from the baseline values in re-lation to the observed time intervals from 10 to 30 min after aortic declamping. In contrast to this, its level in the PUFAs group of patients steadily increased during that time.
Figure 4 shows the increment tendencies of TnT (plate A) and CK-MB values (plate B) in both groups of patients. However, they were less pronounced in both cases in the PUFAs group of patients.
Peri- and postoperative complicatons
Postoperative complications were similar in both groups of patients. In the control group, one patient died of cardiac failure on the second postoperative day, two patients
Fig. 2 – Mean values of serum troponin I (A) and creatine kinase myocardial band (CK-MB) (B) in the control and the poly-unsaturated fatty acids (PUFAs) group of patients subjected to cardiopulmonary bypass (CPB); T0 – before the surgery;
T1 – 4 h after surgery; T2 – 24 h after surgery; *statistically significant difference (p < 0.05).
-1 -0 .8 -0 .6 -0 .4 -0.2 0 0 .2 0 .4 0 .6 0 .8 1
Control group PUFAs group
p<0.0001 p<0.001
Co
eff
ic
ie
n
t
o
f
co
rr
el
at
io
n
(r) v
al
u
es
A
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Control PUFAs
n.s.
p<0.001
Coeff
ic
ie
nt
of c
o
rre
lat
ion (
r) va
lu
es
B
Fig. 3 – Coefficients of correlation between the initial (basal) values and trends in combined values of lactate (A) and oxygen (B) extraction in the control and the polyunsaturated fatty acids (PUFAs) group of patients observed 10 min, 20 min and 30
had perioperative infarction, three patients needed inotropic support. In the PUFAs group, one patient underwent reexplo-ration for bleeding, one had a respiratory failure and two pa-tients needed inotropic support. Due to the low number of the observed complications, no statistical comparison was performed.
Discussion
The results of our prospective, randomized placebo-controlled study in the two groups of adult patients subjected to CPB showed that the extraction of oxygen and the uptake of lactate were markedly increased in the PUFAs pretreated patients compared to the control group, with the subsequent decrease of serum TnT and CK-MB levels in the PUFAs group, pointing thus to their important cardioprotective ef-fect.
Due to the two separate groups of results dealing with oxygen extraction and lactate uptake from one, to the serum levels of TnT and CK-MB to the other side, discussion is di-vided in two parts: the influence of PUFAs on oxygen ex-traction and lactate uptake, and their influence on TnT and CK-MB serum levels.
The influence of PUFAs on oxygen extraction and lactate uptake
Evaluation of myocardial metabolism during cardiac surgery allows the investigator to quantify the degree of physiologic impairment. Direct cannulation of the coronary sinus for coronary sinus blood sampling to measure metabo-lites or specific biochemical markers of myocardial damage has been shown to be a valid tool to define the degree of such impairment 27–29. One of the most sensitive markers of inadequate preservation of the myocardium is the develop-ment of myocardial tissue acidosis and lactate production 30.
We demonstrated in this study that omega-3 PUFAs in-travenous pretreatment prepared the heart metabolically for is-chemia and led to an earlier shift to aerobic metabolism during reperfusion, as indicated by earlier lactate uptake. In this re-spect, the level of lactate extraction 10 and 20 min after aortic declamping had negative values in the control group compared to the positive values in the PUFAs group indicating lactate
uptake. The extraction of oxygen in the PUFAs treated pa-tients was highly statistically significant at all three observed times after CPB in relation to the control group, increasing thus metabolic activity enabled by an increased supply of ex-tracted lactate. Early lactate uptake in the PUFAs group is an index of more rapid recovery of aerobic metabolism, pointing to the improved cardioprotection in our patients. Otherwise, a persistent lactate release during reperfusion in the control group suggests a delayed recovery of aerobic metabolism and may be related to intraoperative inadequate myocardial pro-tection 31. In contrast to this, a significant evidence shows that preserving or enhancing aerobic metabolism, or both, is a key in maintaining cardiac function after ischemia 32–34.
The influence of PUFAs on TnT and CK-MB serum levels
Intraoperative release of TnT and CK-MB has func-tional significance because it is closely related to ischemia time and reflects a delayed recovery of left ventricular func-tion and oxidative metabolism. Therefore, their measurement can be used as an indicator of myocardial injury sustained during CABG 29, 35–37.
This study demonstrated that the intravenous admini-stration of omega-3 PUFAs before CPB statistically signifi-cantly decreased the level of TnT in the PUFAs treated pa-tients in relation to the control group at both observed times, being 58.5% and 46.4% lower at 4 h and 24 h after CPB, re-spectively. (Figure 2 A and B). At the same time, the serum level of CK-MB was also reduced in the PUFAs treated pa-tients at both observed time intervals of 4 h and 24 h after CPB amounting 60.9% and 68.9 %, respectively, in relation to the control group of patients.
The study demonstrated for the first time that acute in-travenous administration of omega-3 emulsion, which is normally used as a part of parenteral nutrition regimens, was associated with a significant reduction in myocardial ische-mic-reperfusion injury. At least a part of this effect could be ascribed to the findings that the ischemic preconditioning actually increases the content of the omega-3 fatty acid DHA in the myocardial membrane in advance of a further injury 38, reduces myocardial oxygen demand, and attenuates acidosis and lactate accumulation in the ischemic heart 39.
-1 0 .8 0 .6 0 .4 0 .2 0 0 .2 0 .4 0 .6 0 .8 1
Control group PUFAs group
p<0.001
p<0.01
A
-1 -0.8 -0.6 -0.4 -0.2 0 0 .2 0 .4 0 .6 0 .8 1
Control group PUFAs group p<0.001 p<0.01
B
Fig. 4 – Coefficients of correlation between the initial (basal) values and trends in combined values of serum troponin I (A) and creatine kinase myocardial band (CK-MB) (B) in the control and the polyunsaturated fatty acids (PUFAs) group of
At molecular level, a special attention in PUFAs car-dioprotective effect should be devoted to their high ROS scavenger potential. Namely, the susceptibility of fatty acids to oxidation is thought to be directly dependent on their de-gree of saturation. Fatty acid micelles scavenge superoxide in an unsaturation dependent manner, up to EPA, which is the most effective fatty acid 40. From a mechanistic view-point, NAD(P)H oxidase is one of the major contributors to endothelial free radical production: its inhibition by DHA 22 and (presumably) other PUFAs, might greatly explain the observed effects on ROS production. DHA-mediated inhibi-tion of IL-1-induced ROS producinhibi-tion would also contribute to the anti-inflammatory actions of omega-3 fatty acids at the endothelial level. One additional mechanism of PUFAs ac-tion would be that they act as a “sink” to trap free radicals, hence becoming oxidized themselves.
Myocardial reperfusion injury is a complex process with inadequately understood mechanisms and multiple initi-ating factors. Therefore, instead targeting some specific dis-turbances, many different pharmacological compounds have been tested not on a genuine, but rather on a screening basis.
All together, the results of such treatments may be di-vided in two groups: with no or modest outcome and positive findings which deserve further study.
The first group concerns adenosine, Ca2+-channel an-tagonists, corticosteroids, NAC, diazoxide, L-arginine, caripo-ride, isoflurane, sevoflurane and nicorandil. So for example, adenosine reduced the levels of TnT, IL-6 and IL-8 release, but was without an effect on the CK-MB level 41. Corticoster-oids had no beneficial effect on mortality and cardiac and pulmonary complications 13, NAC appears to be promising, but increases postsurgical cardiac complications 42, while the levels of TnT and CK-MB were higher in isoflurane compared to sevoflurane group of patients 43. Glucose-insulin-potassium improved hemodynamic parameters, but no significant effect on plasma TnT levels was demonstrated 44, and may cause se-vere disturbances in glucose homeostasis 45, which in case of hyperglycemia may enhance oxidative stress and exacerbate myocardial infarction during reperfusion 46, 47.
In the second studied group, encouraging results were reported with the use of pexelizumab, which in the CPB pa-tients decreased the level of CK-MB and protected against myocardial injury 48, and coenzyme Q10, which increased protection of mitochondria and myofilaments against oxida-tive stress, with a consequent maintenance of energy pro-duction and improved contractile recovery of pectinate tra-beculae isolated from patients receiving coenzyme Q10 after reoxygenaton stress invitro11.
According to these results and taking into account the favorable cardioprotective effects of PUFAs in CPB in our patients, it seems appropriate to consider their combination with coenzyme Q10. Coenzyme Q10 is a physiological con-stituent, declining in synthesis with age. It is an antioxidant and cofactor for mitochondrial ATP generation, basic source of energy in all cells, including myocardial ones. At least, such a combination could fulfill two fundamental require-ments for myocardial membrane and cell function after car-dioplegia and reperfusion oxygenation in CPB patients: pro-tection by dramatic increase in the omega-3 content of myo-cardial membrane phospholipids 20, scavenging ROS, and accompanied by direct effects on ion channels modulating the protein kinase C activity by PUFAs 19, and by improving mitochondrial efficiency with coenzyme Q10.
Although we found significantly different results be-tween the PUFAs group and the control group of patients in terms of myocardial injury in the favor of the first, there are still a few limitations of this study: our investigation was per-formed in a small size sample and with a limited number of clinical events; because of our research fund shortage, we did not use pulmonary artery catheter for monitoring hemody-namics; therefore, we were limited in recording changes between the two groups in myocardial function, and sam-pling method from coronary sinus does not represent global changes in heart metabolism.
Conclusion
PUFAs therapy administered before CPB promotes early metabolic recovery of the heart during elective CABG and leads to better myocardial protection. This study shows that an omega-3 PUFAs emulsion should not be considered only as a nutritional supplement but also as a potentially clinically safe cardioprotective agent. This strategy warrants further investigation with optimization and shortening of pretreatment regimens to be more clinically applicable. It would be of interest to perform a larger randomized study with a design similar to the present study.
Acknowledgments
We would like to present our appreciation and thanks to prof. Bogdan Boškoviü who provided research support and was an active participant in the preparation of this manuscript.
Declaration of conflicting interests
The authors declared no conflicts of interest with re-spect to the authorship and/or publication of this article.
R E F E R E N C E S
1. Murphy E, Steenbergen C. Mechanisms underlying acute protec-tion from cardiac ischemia-reperfusion injury. Physiol Rev 2008; 88(2): 581î609.
2. Salis S, Mazzanti VV, Merli G, Salvi L,Tedesco CC, Veglia F, et al. Cardiopulmonary Bypass Duration Is an Independent Pre-dictor of Morbidity and Mortality After Cardiac Surgery. J Cardiothorac Vasc Anesth 2008; 22(6): 814î22.
3. Ngaage DL, Cowen ME, Cale AR. Cardiopulmonary bypass and left ventricular systolic dysfunction impacts operative mortality differently in elderly and young patients. Eur J Cardiothorac Surg 2009; 35(2): 235î40.
5. Teshima Y, Akao M, Jones SP, Marbán ECariporide (HOE642), a selective Na+-H+ exchange inhibitor, inhibits the mitochon-drial death pathway.Circulation 2003; 108(18): 2275î81. 6. Lell WA, Nielsen VG, McGiffin DC, Schmidt FE Jr, Kirklin JK,
Stanley AW. Glucose-insulin-potassium infusion for myocar-dial protection during off-pump coronary artery surgery. Ann Thorac Surg 2002; 73(4): 1246–52.
7. Jin Z , Duan W, Chen M, Yu S, Zhang H, Feng G, et al. The myocardial protective effects of adenosine pretreatment in children undergoing cardiac surgery: a randomized controlled clinical trial. Eur J Cardiothorac Surg 2011; 39(5): e90î6. 8. Wijeysundera DN, Beattie WS, Rao V, Karski J. Calcium
antago-nists reduce cardiovascular complications after cardiac surgery: a meta-analysis. J Am Coll Cardiol 2003; 41(9): 1496î505. 9. Carrier M, Pellerin M, Perrault LP, Bouchard D, Page´P , Searle N,
et al. Cardioplegic Arrest With L-Arginine Improves Myocar-dial Protection: Results of a Prospective Randomized Clinical Trial. Ann Thorac Surg 2002; 73(3): 837– 42.
10.El-Hamamsy I, Stevens LM, Carrier M, Pellerin M, Bouchard D, Demers P, et al. Effect of intravenous N-acetylcysteine on out-comes after coronary artery bypass surgery: A randomized, doubleblind, placebo-controlled clinical trial. J Thorac Cardio-vasc Surg 2007; 133(1): 7î12.
11.Rosenfeldt F, Marasco S, Lyon W, Wowok M, Sheeran F, Bailey M,
et al. Coenzime Q 10 therapy before cardiac surgery improves myocardial function and in vitro contracrility of myocardial tis-sue. J Thorac Cardiovasc Surg 2005; 129(1): 25î32.
12.Deja MA, Malinowski M, Golba KS, Kajor M, Lebda-Wyborny T, Hudziak D, etal. Diazoxide protects myocardial mitochondria, metabolism, and function during cardiac surgery: A double-blind randomized feasibility study of diazoxide-supplemented cardioplegia and Na/H exchange inhibitors. J Thorac Cardio-vasc Surg, 2009; 137(4): 997î1004, 1004eî2.
13.Dieleman JM, van Paassen J, van Dijk D, Arbous MS, Kalkman CJ, VandenbrouckeJP,et al. Prophylactic corticosteroids for cardio-pulmonary bypass in adults. Cochrane Database Syst Rev 2011; (5): CD005566.
14.Smith PK, Carrier M, Chen JC, Haverich A, LevyJH, Menasché P, et al. Effect of Pexelizumab in Coronary Artery Bypass Graft Surgery With Extended Aortic Cross-Clamp Time. Ann Tho-rac Surg 2006; 82(3): 781–9.
15.Laurent G, Moe G, Hu X, Holub B, Leong-Poi H, Trogadis J, et al. Long chain n-3 polyunsaturated fatty acids reduce atrial vul-nerability in a novel canine pacing model. Cardiovasc Res 2008; 77(1): 89–97.
16.Li GR, Sun HY, Zhang XH, Cheng LC, Chiu SW, Tse HF, et al. Omega-3 polyunsaturated fatty acids inhibit transient outward and ultra-rapid delayed rectifier K1currents and Na1current in human atrial myocytes. Cardiovasc Res 2009; 81(2): 286–93. 17.McGuinness J, Byrne J, Condron C, McCarthy J, Bouchier-Hayes D,
Redmond JM. Pretreatment with omega-3 fatty acid infusion to prevent leukocyte-endothelial injury responses seen in cardiac surgery. J Thorac Cardiovasc Surg 2008; 136(1): 135î41. 18.Wang R, Kern JT, Goodfriend TL, Ball DL, Luesch H. Activation
of the antioxidant response element by specific oxidized me-tabolites of linoleicacid. Prostaglandins Leukot Essent Fatty Acids 2009; 81(1): 53î9.
19.Le Guennec JY, Jude S, Besson P, Martel E, Champeroux P. Cardio-protection by omega-3 fatty acids: involvement of PKCs? Prostaglandins Leukot Essent Fatty Acids 2010; 82(4î6): 173î7.
20.McGuinness J, Neilan TG, Sharkasi A, Bouchier-Hayes D, Redmond JM. Myocardial protection using an omega-3 fatty acid infu-sion: quantification and mechanism of action. J Thorac Car-diovasc Surg 2006; 132(1): 72î9.
21.Richard D, Kefi K, Barbe U, Bausero P, Visioli F. Polyunsaturated fatty acids as antioxidants. Pharmacol Res 2008; 57(6): 451î5.
22.Massaro M, Habib A, Lubrano L, Turco SD, Lazzerini G,Bourcier T,et al. The omega-3 fatty acid docosahexaenoate attenuates endothelial cyclooxygenase-2 induction through both NADP(H) oxidase and PKC epsilon inhibition. Proc Natl Acad Sci USA 2006; 103(41): 15184–9.
23.Nodari S, Triggiani M, Campia U, Manerba A, Milesi G, Cesana BM, et al. Effects of n-3 polyunsaturated fatty acids on left ventricular function and functional capacity in patients with dilated cardiomyopathy. J Am Coll Cardiol 2011; 57(7): 870–9. 24.Mayyas F, Sakurai S, Ram R, Rennison JH, Hwang ES, Castel L, et
al Dietary ƹ3 fatty acids modulate the substrate for post-operative atrial fibrillation in a canine cardiac surgery model. Cardiovasc Res 2011; 89(4): 852î61.
25.Bianconi L, Calò L, Mennuni M, Santini L, Morosetti P, Azzolini P,
et al. n-3 polyunsaturated fatty acids for the prevention of ar-rhythmia recurrence after electrical cardioversion of chronic persistent atrial fibrillation: a randomized, double-blind, mul-ticentre study.Europace 2011; 13(2): 174î81.
26.Wollert HG, Müller W, Fischer D, Wollert U, Panzner R, Schubert F, et al.Perioperative assessment of cardiac energy metabolism by means of arterio-coronary venous difference in lactate con-centration (acDL). A parameter for optimizing ventricular function of the postcardioplegic myocardium. Eur J Cardio-thorac Surg 1990; 4(5): 278î83.
27.Siouffi SY, Kwasnik EM, Khouri SF. Methods for the metabolic quantification of regional myocardial ischemia. J Surg Res 1987; 43(4): 360–78.
28.Vijay P, Szekely L, Aufiero TX, Sharp TG. Coronary sinus adre-nomedullin rises in response to myocardial injury. Clin Sci (Lond) 1999; 96(4): 415î20.
29.Koh TW, Hooper J, Kemp M, Ferdinand FD, Gibson DG, Pepper JR.
Intraoperative release of troponin T in coronary venous and arterial blood and its relation torecovery of left ventricular function and oxidative metabolism following coronary artery surgery. Heart 1998; 80(4): 341î8.
30.Crittenden MD. Intraoperative metabolic monitoring of the heart: I. Clinical assessment of coronary sinus metabolites. Ann Thorac Surg. 2001; 72(6): S2220î6; discussion S2267î70. 31.Rao V, Ivanov J, Weisel RD, Cohen G, Borger MA, Mickle DA.
Lactate release during reperfusion predicts low cardiac output syndrome after coronary bypass surgery. Ann Thorac Surg 2001; 71(6): 1925î30.
32.Shinde SB, Golam KK, Kumar P, Patil ND. Blood lactate levels during cardiopulmonary bypass for valvular heart surgery. Ann Card Anesth 2005; 8(1): 38î44.
33.Kapoor PM, Mandal B, Chowdhury UK, Singh SP, Kiran U. Changes in myocardial lactate, pyruvate and lactate-piruvate ratio during cardiopulmonary bypass for elective adult cardiac surgery: Early indicator of morbidity. J Anesth Clin Pharmac 2011; 27(2): 225î32.
34.Onorati F, Cristodoro L, Caroleo S, Esposito A, Amantea B, Santan-gelo E, et al. Troponin I and lactate from coronary sinus predict cardiac complications after myocardial revascularization. Ann Thorac Surg 2007; 83(3): 1016–23.
35.Rousou LJ, Crittenden MD,Taylor KB, Healey NA, Gibson S, Thatte HS, et al. Troponin I after cardiac surgery and its implications on myocardial protection, outcomes, and cost. Am J Surg 2008; 196(5): 703–9.
36.Mohiti J, Behjati M, Soltani MH, Babaei A. The significance of troponin T and CK-MB release in coronary bypass surgery. Ind J Clin Bioch 2004; 19(1): 113î7.
37.Mohammed AA, Agnihotri AK, van Kimmenade RRJ, Martinez-Rumayor A, Green SM, Quiroz R, et al. Prospective, comprehen-sive assessment of cardiac troponin T testing after coronary artery bypass graft surgery. Circulation 2009; 120(10): 843î50. 38.Starkopf J, Andreasen TV, Bugge E, Ytrehus K. Lipid peroxidation,
ischaemic preconditioning of rat heart. Cardiovasc Res 1998; 37(1): 66î75.
39.Pepe S, McLennan PL. Cardiac membrane fatty acid composi-tion modulates myocardial oxygen consumpcomposi-tion and post-ischemic recovery of contractile function. Circulation 2002; 105(19): 2303î8.
40.Richard D, Kefi K, Barbe U, Bausero P, Visioli F. Polyunsaturated fatty acids as antioxidants. Pharmacol Res 2008; 57(5): 451–5. 41.Liu R, Xing J, Miao N, Li W, Liu W, Lai YQ, et al. The
myo-cardial protective effect of adenosine as an adjunct to inter-mittent blood cardioplegia during open heart surgery. Eur J Cardiothorac Surg 2009; 36(6): 1018î23.
42.Baker WL, Anglade MW, Baker EL, White CM, Kluger J, Coleman CI. Use of N-acetylcysteine to reduce post-cardiothoracic sur-gery complications: a meta-analysis. Eur J Cardiothorac Surg 2009; 35(3): 521î7.
43.Ceyhan D, TanrÖverdi B, Bilir A. Comparison of the effects of sevoflurane and isoflurane on myocardial protection in coro-nary bypass surgery. Anadolu Kardiyol Derg 2011; 11(3): 257î62.
44.Howell JN, Ashrafian H, DPhil, Drury NE, Ranasinghe AM, Con-tractor H, et al.Glucose-Insulin-Potassium Reduces the Inci-dence of Low Cardiac Output Episodes After Aortic Valve
Replacement for Aortic Stenosis in Patients With Left Ven-tricular Hypertrophy: Results From the Hypertrophy, Insulin, Glucose, and Electrolytes (HINGE) Trial. Circulation 2011; 123(2): 170î7.
45.Gradinac S, Coleman GM, Taegtmeyer H, Sweeny MS, Frazier OH.
Improved cardiac function with GIK after aorto-coronary by-pass grafting. Ann Thorac Surg 1989; 48: 284–9.
46.Yang Z, Laubach VE, French BA, Kron IL. Acute hyperglycemia enhances oxidative stress and exacerbates myocardial infarc-tion by activating nicotinamide adenine dinucleotide phos-phate oxidase during reperfusion. J Thorac Cardiovasc Surg 2009; 137(3): 723î9.
47.Albacker TB, Carvalho G, Schricker T, Lachapelle K. Myocardial Protection During Elective Coronary Artery Bypass Grafting Using High-Dose Insulin Therapy. Ann Thorac Surg 2007; 84(6): 1920–7.
48.Smith PK, Carrier M, Chen JC, Haverich A, LevyJH, Menasché P, et al. Effect of Pexelizumab in Coronary Artery Bypass Graft Surgery With Extended Aortic Cross-Clamp Time. Ann Tho-rac Surg, 2006; 82(3): 781–9.
